Conventional photodiode arrays are disclosed in Patent Literatures 1 and 2, for example. A photodiode array, such as SiPM (Silicon Photo Multiplier) or PPD (Pixelated Photon Detector), has a structure in which APDs (avalanche photodiodes) are arranged in a matrix shape, a plurality of APDs are connected in parallel, and a sum of outputs of the APD is read. When an APD is operated in the Geiger mode, a feeble light (photon) can be detected. That is, when a photon enters the APD, a carrier generated in the APD is output to the outside through a quenching resistor and a wiring pattern for reading a signal. Although electric current flows through a pixel in which an electron avalanche in an APD has occurred, a voltage drop occurs through a quenching resistor of about hundreds kΩ sequentially connected to the pixel. This voltage drop lowers the voltage applied to an amplification region of the APD, which terminates a multiplication effect by the electron avalanche. In this manner, one pulse signal is output from an APD in response to an incidence of one photon.    Patent Literature 1: European Patent Application Publication No. 1755171    Patent Literature 2: U.S. Patent Application Publication No. 2006/175529